<head>
<meta charset="utf-8">
    <title>javascript 简单计算器</title>
    <script>
        //定义全局变量         var one="1";
        var two="2";
        var three="3";
        var four="4";
        var five="5";
        var six="6";
        var seven="7";
        var eight="8";
        var nine="9";
        var zero="0";
         var plus="+",minus="-",multiply="*",divide="/",decimal=".";
         function enter(obj,string){
                obj.expr.value+=string;
            }
         function compute(obj){
              }
  </script>
</head>
<body>
    <form name="calc" id="calc" action="">
        <table border="1">
        <td colspan="4"><input type="text" name="expr" size="30" action="compute(this.form)" /></td>
        <tr>
        <td><input type="button" value=" 7 " onclick="enter(this.form,seven)" /></td>
        <td><input type="button" value=" 8 " onclick="enter(this.form,eight)" /></td>
        <td><input type="button" value=" 9 " onclick="enter(this.form,nine)" /></td>
        <td><input type="button" value=" / " onclick="enter(this.form,divide)" /></td>
        </tr>
        <tr>
        <td><input type="button" value=" 4 " onclick="enter(this.form,four)" /></td>
        <td><input type="button" value=" 5 " onclick="enter(this.form,five)" /></td>
        <td><input type="button" value=" 6 " onclick="enter(this.form,six)" /></td>
        <td><input type="button" value=" * " onclick="enter(this.form,multiply)" /></td>
        </tr>
        <tr>
        <td><input type="button" value=" 1 " onclick="enter(this.form,one)" /></td>
        <td><input type="button" value=" 2 " onclick="enter(this.form,two)" /></td>
        <td><input type="button" value=" 3 " onclick="enter(this.form,three)" /></td>
        <td><input type="button" value=" - " onclick="enter(this.form,minus)" /></td>
        </tr>
        <tr>
        <td colspan="2"><input type="button" value=" 0 " onclick="enter(this.form,zero)" /></td>
        <td><input type="button" value=" . " onclick="enter(this.form,decimal)" /></td>
        <td><input type="button" value=" + " onclick="enter(this.form,plus)" /></td>
        </tr>
        <tr>
        <td colspan="2"><input type="button" value=" = " onclick="compute(this.form)" /></td>
        <td colspan="2"><input type="button" value="AC" onclick="form.reset()"/></td>
        </tr>
        </table>
</form>
</body>
</html>
